<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>clear2</title>
    <style>
        .box {
            border: 1px solid red;
        }
        .item {
            width: 200px;
            height: 200px;
            background-color: black;
            float: left;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="item"></div>
    </div>
</body>
</html>